Search

Ti-rich PbZr1-xTixO3 (x = 0.65, PZT65) single crystals with the dimensions of 1 × 1 × 0.2 mm3 were grown by the self-flux method. Micron-sized ferroelectric domains were observed and characterized via piezoresponse force microscopy (PFM) and switching spectroscopy PFM. Both out-of-plane and in-plane components of polarization were obtained by detecting vertical and lateral vibrations of the PFM cantilever. The piezoresponse image examination revealed a clear lamellar domain structure due to apparent twinning and the formation of 90° domains. A negative self-polarization was observed in the studied crystals leading to the asymmetry of piezoresponse hysteresis loops and the polarization imprint. The polarization switching mechanism under the external electric field applied via a PFM tip was investigated. The 90° domain wall width was determined from the local PFM measurements and tentatively attributed to the oblique domain walls and chemical disorder. The time-dependent PFM imaging revealed a slow polarization relaxation process with a characteristic time of about 200 min. [ABSTRACT FROM AUTHOR]

The dielectric properties of Mn-doped ZnO ceramics with electrically active grain boundaries at low temperatures of 10-70 K were investigated by admittance spectroscopy. It was observed that the dielectric relaxation of the main shallow donors, zinc interstitial, in these samples occurred in the temperature range of 20-50 K. Based on theoretical analysis, an expression for the admittance of an electrically active grain boundary at low temperatures was obtained. It was concluded that the relaxation of the shallow donors is Debye type with a thermally activated relaxation time and is related to the ionization process of these donors. The activation energy for the relaxation, i.e., the ionization energy of the shallow donors, was determined to be about 0.04 eV, the capture cross section of the shallow donors to be around 10[sup -12] cm², and the relaxation time at room temperature to be about 10[sup -13] s. [ABSTRACT FROM AUTHOR]

The sequence of structure transformations, P2 1 / n - I 2/ m - Fmm , involving oxygen octahedral tilting has been revealed in the ceramics of the whole-range B -site ordered perovskite system ( 1 - x )La(Mg 1/2 Ti 1/2 )O 3 - x Ba(Mg 1/2 W 1/2 )O 3 . Microwave dielectric characteristics of the ceramics have been evaluated as a function of their composition. The observed structure sequence and structure-dependent dielectric behavior are discussed in respect to an order of the transition between anti-phase tilted and untilted configurations as well as a likely clustering in the system. [ABSTRACT FROM AUTHOR]

The intermediate stage sintering kinetics of undoped ZnO and ZnO doped with 0.1–1.2 mol% Mn were investigated. It was found that the densification in the initial and intermediate stages is affected by surface diffusion in both undoped and Mn-doped ZnO, and that this contribution increases with the increase in the Mn content. The surface diffusion causes an initial pore growth, a more significant grain growth, and an apparent increase in the activation energy for densification at lower densities. Further kinetic analysis showed that the densification process in the intermediate stage is dominated by volume diffusion in all the compositions. The calculated values of the diffusion coefficients are consistent with the ones obtained by the tracer diffusion measurements of Zn in ZnO crystals in other works. The origin of the increase of the surface transport is discussed, together with its effect on the second phase mobility. [ABSTRACT FROM AUTHOR]